1. Field of the Invention
This invention relates to indicating devices for being attached to balancing scales, and in particular to an indicating device including means for adjusting the fine zero balance of balance beam scales.
2. Description of the Prior Art
Attachments for weighing scales of the balance beam type are well known in the art. These indicating devices allow the operator to accurately observe when the balance beam has achieved a balancing condition without the necessity of straining ones eyes or sighting along the longitudinal axis of the balance beam. The over/under nomenclature has become standard for indicating to the operator whether additional material must be added to or subtracted from the bulk material being weighed. These attachments may be used on any type of balance beam scale, including the more common gravity and spring operated designs.
However, previous designs have required extensive set up and calibration procedures which often affect the critical fine balancing mechanisms of the balance beam scale. Furthermore, when the scale is moved or even accidentally jarred, the balance beam zero adjustment is often displaced and the operator must then laboriously proceed through the entire balancing and rezeroing process again. It is an object of this invention to include with the over/under indicating attachment for a balance beam scale the additional feature of a zeroing control for simultaneously adjusting the over/under indicator device and the balancing beam scale to a balancing condition.
J. M. Spinks in U.S. Pat. No. 1,576,375 discloses an over/under indicating attachment for balance beam scales, with the over/under indicator including a balancing lever mounted off center on the frame and a connecting rod connected at one end to the balance beam and pivotally connected at the other end to the balancing lever. An indicator is carried by the balancing lever and moves adjacent to a chart for indicating the balancing or over/under condition.
Other over/under indicator devices for balancing beam scales are disclosed by Singleton, in U.S. Pat. No. 2,659,593; Hale et al in U.S. Pat. No. 3,031,021; and Hamblin et al. in U.S. Pat. No. 1,800,017. In general, these prior art inventions utilize a static balancing technique which is not readily adaptable for repeated rapid rebalancing.
Other over/under indicators already incorporated into balancing beam scales are disclosed by Fate in U.S. Pat. No. 2,467,300; Breaden in U.S. Pat. No. 2,032,910; Breaden in U.S. Pat. No. 1,896,281; Hadley in U.S. Pat. No. 1,759,900; and Marer in U.S. Pat. No. 876,986.